(CNN) -- The United States will not accept North Korea as a nuclear-armed state, Defense Secretary Robert Gates said Saturday at an international conference.

South Korean sailors take part in exercises Friday in disputed waters off the Korean Peninsula.

"We will not stand idly by as North Korea builds the capability to wreak destruction on any target in the region -- or on us," said Gates, speaking at the International Institute for Strategic Studies in Singapore.

"Our goal is complete and verifiable denuclearization of the Korean Peninsula, and we will not accept North Korea as a nuclear weapons state," he said.

His comments came amid growing concern across the globe over North Korea's latest nuclear test and test-firings of short-range missiles.

On Friday, two Defense Department officials said the latest U.S. satellite imagery has spotted "vehicle activity" at a North Korean ballistic missile facility.

"North Korea's nuclear program and actions constitute a threat to regional peace and security. We unequivocally reaffirm our commitment to the defense of our allies in the region," Gates said in Singapore. Watch what Gates thinks of crisis »

The United States would hold North Korea "fully accountable for the consequences" if the secretive state were to provide nuclear weapons or material to other nations or groups, Gates warned.

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North Korea's programs have isolated the country and "quite literally, starved its people," he said.

"Dependent on the charity of the international community to alleviate the hunger and suffering of its people, North Korea's leadership has chosen to focus the North's limited energy and resources on a reckless and ultimately self-destructive quest for nuclear weapons and intercontinental ballistic missiles," Gates said.

He said the administration of President Obama and its allies "are open to dialogue" but won't bend to pressure or provocation.

"And on this count, North Korea's latest reply to our overtures isn't exactly something we would characterize as helpful or constructive," Gates said.

"At the end of the day, the choice to continue as a destitute international pariah or chart a new course is North Korea's alone to make. The world is waiting."